Optical coupling arrangement having low coupling loss and high production yield

Abstract

An optical coupling arrangement has a first transition region having a plurality of first segmented waveguides and a plurality of transverse segments of alternating indices of refraction with at least some of the transverse segments traversing the first segmented waveguides. The first segmented waveguides are formed by core segments in some of the transverse segments. The arrangement may also have a second transition region having a plurality of second segmented waveguides each aligned with a respective one of the first segmented waveguides. The arrangement is manufactured with a high production yield and is used in an optical coupling device for combining/splitting optical signals to reduce the insertion loss. The optical coupling device is also used in other devices such as Mach-Zehnder devices and arrayed waveguide grating demultiplexers/multiplexers.

1. An optical coupling arrangement comprising:
 a first transition region comprising:  
 a plurality of first segmented waveguides; and  
 a plurality of transverse segments of alternating indices of refraction, at least some of the transverse segments traversing the first segmented waveguides,  
 wherein the first transition region is delimited by the transverse segments and wherein the transverse segments and individual ones of the first segmented waveguides are adapted to provide mode expansion and mode contraction, respectively, in respect to a direction traversing the transverse segments.  
 
   
   
     2. An optical coupling arrangement according to  claim 1  wherein the plurality of transverse segments of alternating indices of refraction comprise a plurality of first transverse segments of a core material and a plurality of second transverse segments of a cladding material, the first transverse segments being interleaved with the second transverse segments. 
   
   
     3. An optical coupling arrangement according to  claim 2  wherein the first transition region has a first end and a second end with said direction traversing from first end to the second end and wherein for each one of the first transverse segments having a next first transverse segment of the first transverse segments which is farther from the first end than said one of the first transverse segments, a ratio of a width of said one of the first transverse segments to a total width of said one of the first transverse segments and an adjacent one of the second transverse segments is greater than or equal to a ratio of a width of said next first transverse segment to a total width of said next first transverse segment and an adjacent one of the second transverse segments. 
   
   
     4. An optical coupling arrangement according to  claim 2  wherein the first transition region has a first end and a second end with said direction traversing from first end to the second end and wherein for each one of the first transverse segments having a next first transverse segment of the first transverse segments which is farther from the first end than said one of the first transverse segments, a width of said one of the first transverse segments is greater than or equal to a width of said next first transverse segment. 
   
   
     5. An optical coupling arrangement according to  claim 2  wherein the first transition region has a first end and a second end with said direction traversing from first end to the second end and wherein for each one of the second transverse segments having a next second transverse segment of the second transverse segments which is farther from the first end than said one of the second transverse segments, a width of said one of the second transverse segments is less than or equal to a width of said next second transverse segment. 
   
   
     6. An optical coupling arrangement according to  claim 2  where the first segmented waveguides are formed by core segments in at least some of the second transverse segments. 
   
   
     7. An optical coupling arrangement according to  claim 6  wherein the core segments are protrusions each extending from a respective one of the first transverse segments. 
   
   
     8. An optical coupling arrangement according to  claim 6  wherein the first transition region has a first end and a second end with said direction traversing from first end to the second end and wherein for each one of the second transverse segments having said core segments and having a next second transverse segment of the second transverse segments which also has said core segments and which is farther from the first end than said one of the second transverse segments, a width of said core segments of said one of the second transverse segments is less than or equal to a width of said core segments of the next second transverse segment. 
   
   
     9. An optical coupling arrangement according to  claim 6  wherein the first transition region has a first end and a second end with said direction traversing from first end to the second end and wherein for each one of the second transverse segments having said core segments and having a next second transverse segment of the second transverse segments which also has said core segments and which is farther from the first end than said one of the second transverse segments, a ratio of a width of said core segments of said one of the second transverse segments to a width of said one of the second transverse segments is less than or equal to a ratio of a width of said core segments of said next second transverse segment to a width of said next second transverse segment. 
   
   
     10. An optical coupling arrangement according to  claim 1  comprising:
 a second transition region coupled to the first transition region in a manner that said direction traverses from the first transition region to the second transition region, the second transition region having a plurality of second segmented waveguides each aligned with a respective one of the first segmented waveguides of the first transition region.  
 
   
   
     11. An optical coupling arrangement according to  claim 10  wherein the second transition region has a first end and a second end with said direction traversing from first end to the second end and wherein, in the second transition region, each one of the second segmented waveguides comprises a plurality of first longitudinal segments of a core material and a plurality of second longitudinal segments interleaved with the first longitudinal segments, the second longitudinal segments having an index of refraction which is different than the index of refraction of the core material. 
   
   
     12. An optical coupling arrangement according to  claim 11  wherein the second transition region has a first end and a second end with said direction traversing from first end to the second end and wherein within a second segmented waveguide of the second segmented waveguides, a ratio of a width of a first longitudinal segment of the first longitudinal segments to a total width of said first longitudinal segment and an adjacent one of the second longitudinal segments is less than or equal to a ratio of a width of a next first longitudinal segment of the first longitudinal segments to a total width of said next first longitudinal segment and an adjacent one of the second longitudinal segments, the next first longitudinal segment being located farther from the first end than said first longitudinal segment. 
   
   
     13. An optical coupling arrangement according to  claim 11  wherein the second transition region has a first end and a second end with said direction traversing from first end to the second end and wherein within a second segmented waveguide of the second segmented waveguides, a width of a first longitudinal segment of the first longitudinal segments is less than or equal to a width of a next first longitudinal segment of the first longitudinal segments, the next first longitudinal segment being located farther from the first end than said first longitudinal segment. 
   
   
     14. An optical coupling arrangement according to  claim 11  wherein the second transition region has a first end and a second end with said direction traversing from first end to the second end and wherein within each second segmented waveguide of the second segmented waveguides, a total width of a first longitudinal segment of the first longitudinal segments and an adjacent one of the second longitudinal segments is less than or equal to a total width of a next first longitudinal segment of the first longitudinal segments and an adjacent one of the second longitudinal segments, the next first longitudinal segment being located farther from the first end than said first longitudinal segment. 
   
   
     15. An optical coupling arrangement according to  claim 1  comprising:
 a first array of first waveguides which is arranged to be coupled through to the first transition region in a manner that said direction traverses from the first transition region to the first array, wherein each one of the first waveguides of the first array is aligned with a respective one of the first segmented waveguides of the first transition region.  
 
   
   
     16. An optical device for combining/splitting optical signals comprising the optical coupling arrangement of  claim 15  and comprising:
 a second array of one or more second waveguides; and  
 a first coupling waveguide for coupling the one or more second waveguides of the second array with the first transition region.  
 
   
   
     17. An optical device according to  claim 16  wherein the first coupling waveguide is a slab waveguide. 
   
   
     18. An optical device according to  claim 16  wherein the first coupling waveguide comprises an end at which the first transition region is coupled, said end comprising protrusions extending perpendicularly from the first coupling waveguide into an adjacent one of the transverse segments, each one of the protrusions being aligned with a respective one of the first segmented waveguides of the first transition region. 
   
   
     19. An optical device according to  claim 16  wherein the device is a star coupler. 
   
   
     20. An AWG (Arrayed Waveguide Grating) demultiplexer/multiplexer comprising two star couplers according to  claim 19 , the AWG demultiplexer/multiplexer further comprising:
 an AWG adapted to couple respective ones of said first waveguides of said first array of the two star couplers each with a respective optical path length.  
 
   
   
     21. A branch power splitter comprising an optical device according to  claim 16  wherein the second array has one second waveguide. 
   
   
     22. A Y-junction comprising a branch power splitter according to  claim 21  wherein the first array has two first waveguides. 
   
   
     23. A Mach-Zehnder interferometer device comprising two Y-junctions according to  claim 22 , the Mach-Zehnder interferometer device further comprising:
 second coupling waveguides each coupling respective nes of said first waveguides of said first array of the two Y-junctions.  
 
   
   
     24. A Mach-Zehnder interferometer device according to  claim 23  comprising a heater adapted to control the optical path length of a second coupling waveguide of the second coupling waveguides. 
   
   
     25. A Mach-Zehnder interferometer device according to  claim 23  comprising an electrical device adapted to apply an electric field to a second coupling waveguide of the second coupling waveguides to control the optical path length of said second coupling waveguide. 
   
   
     26. A Mach-Zehnder interferometer device according to  claim 23  for use as an optical modulator. 
   
   
     27. A Mach-Zehnder interferometer device according to  claim 23  for use as a variable optical attenuator.